The invention generally relates to tube arrangements, in particular to tube arrangements which form crossbeams or which form part of crossbeams, in particular crossbeams used in motor vehicles.
Without any restriction in generality, the tube arrangement according to the invention is described by the example of its use as a crossbeam or as a component of a crossbeam for a motor vehicle. As part of the motor vehicle body, the crossbeam is arranged so as to run approximately horizontally between the A-pillars, as they are known, in the region below the windscreen. The crossbeam serves for fastening the instrument panel, moreover the crossbeam stiffening the instrument panel which usually consists of plastic and/or wooden parts.
The crossbeam must have a high degree of flexural strength not only because of its function of stiffening the instrument panel, but also on account of its function as a body component. High flexural strength of the crossbeam contributes, not least, to the higher safety of the motor vehicle and to protection of the occupants in the event of an accident.
While crossbeams may, in principle, be manufactured from a continuous tube, structural conditions dependent on the vehicle type may make it necessary to construct the crossbeams from a plurality of tubes which must be fixedly connected to one another. Constructing a crossbeam from a tube arrangement which has a plurality of tubes may also be advisable against the background of the avoidance of resonances in the crossbeam when the motor vehicle is being driven. For this purpose, it may be appropriate to produce the crossbeam from a plurality of tubes which have different cross-sectional sizes and/or cross-sectional shapes.
In the context of the present invention, the term “tube” is to be understood in general, and a tube in the context of the present invention may have any desired cross-sectional shape which, for example, may be round, angular or oval. Furthermore, it would be appreciated that, in the tube arrangement according to the invention, the first tube and the second tube may have identical or different cross-sectional shapes and/or cross-sectional sizes. Moreover, the first tube and/or the second tube may not only have a straight run, as seen in the longitudinal direction, but may also have one or more bends. Also, in the region of their connection, the tubes, instead of running parallel to one another, may also run obliquely with respect to one another.
If the crossbeam has a tube arrangement which is assembled from a plurality of tubes, there is basically a problem in the flexion-resistant connection of the individual tubes to one another.
The simplest connection technique for connecting two tubes is to arrange the two tubes side by side so as to partially overlap one another, so that the tubes are in contact in the overlap region, and to weld the two tubes to one another in the overlap region. If the two tubes have a round cross section, however, there is the problem that the two tubes are in contact in the overlap region solely along a generatrix, and the connection of the two tubes is correspondingly limited to a linear weld seam. Such a connection of the two tubes, however, does not have sufficient flexural strength. In order to achieve higher flexural strength with such a connection technique, the overlap region could be enlarged in the longitudinal direction, although, because of the greater length of the two tubes which is required, this may lead to an increased outlay in terms of material and therefore to a higher weight of the tube arrangement, this being undesirable when the tube arrangement is used for a crossbeam in a motor vehicle.
Another possibility for connecting the two tubes of the tube arrangement is to arrange in the overlap region of the two tubes a metal sheet which extends transversely with respect to the longitudinal direction of the two tubes and which is welded to the two tubes, and to arrange, from the respective end of one tube to the other tube, a gusset which extends in the longitudinal direction of the tubes. The gussets, although increasing the flexural strength of the connection of the two tubes, nevertheless have the disadvantage that, if the tube arrangement is used for a crossbeam, they impede the mounting of further structural parts of the crossbeam, in particular tie-up elements, for example for the instrument panel, in the region of the connection of the two tubes.
Furthermore, a connection by means of the connection elements described above has the further disadvantage that the flexural strength is sufficient in only two preferential directions which are determined by the planes of the connecting sheets or gussets, but may be insufficient in other spatial directions. Sufficient flexural strength in a multiplicity of spatial directions would make it necessary, in such a connection technique, to mount further gussets which extend in different directions, which, however, further increases the weight and costs of the tube arrangement.
To be precise, in addition to the requirement for a low weight of a crossbeam for a motor vehicle, it must also be capable of being produced cost-effectively, thus entailing a further restriction in the possibilities for making a flexion-resistant connection of the two tubes.